Lincoln's 3-1 win over Championship leaders Brighton was just one chapter in an enthralling afternoon of football that also saw Wolves dump out Liverpool, Oxford upset Newcastle, and League Two Wycombe come agonisingly close to stunning Tottenham at White Hart Lane.
The fourth-round action led BBC Sport pundit Garth Crooks to proclaim the FA Cup "alive and well".
"It was a magnificent day with some wonderful performances," he said. "Wycombe were sensational, as were Lincoln."
The last time Lincoln reached the last 16 of the FA Cup was in the 1901-02 season, a run that featured a victory over a cash-strapped team from the north-west of England named Newton Heath, who within weeks would be issued with a winding-up order before being saved and renamed Manchester United in April 1902.
The fortunes of those two sides have differed wildly over the past 115 years, but Lincoln at least have the pleasure of knowing their place in the fifth-round draw on Monday evening is already assured, with holders United in action at Wigan on Sunday.
After dominating Ipswich in their third-round replay earlier this month, National League leaders Lincoln faced an altogether sterner task against in-form Brighton, who made nine changes for the game at Sincil Bank but nevertheless deservedly led at the break.
Chris Hughton's visitors went in front through Richie Towell's well-taken strike, but the hosts rallied after the break, levelling through Alan Power's penalty before Fikayo Tomori's own goal gave them the lead.
Theo Robinson, who scored twice at Ipswich in the third round, added the third on the break to confirm the Imps' place in the next round.
"I'm surprised. It's not often football surprises me, but today..." said Lincoln boss Cowley. "I was really pleased that we were able to stay in the game [after going behind].
"It's surreal, and it's been surreal for quite a period of time. The first Ipswich game, seeing those 5,000 away supporters and hearing the noise they made, from that moment onwards it's been crazy - but a good crazy.
"I can't believe the scenes and the emotion and the support."
It was a case of what might have been for brave Wycombe, who led 2-0 and 3-2 before succumbing to a heartbreaking 4-3 loss at White Hart Lane.
Son Heung-min's stoppage-time winner rescued the Premier League side, who were rocked on their heels by Paul Hayes' sweetly struck left-footed volley that put Wycombe ahead.
The captain grabbed his second from the spot to double the visitors' lead before Son's deflected effort on the hour and a Vincent Janssen penalty four minutes later pulled Spurs level.
Substitute Garry Thompson headed in Myles Weston's cross with seven minutes to go to put Gareth Ainsworth's side back in front, but Dele Alli pulled Spurs level again before Son scrambled in a late winner.
"The lads have done me and the town so proud," Wycombe boss Ainsworth said.
"It was an outstanding effort from the boys. I am so proud, disappointed but it is now back to the reality of Exeter away."
At Anfield, Championship strugglers Wolves recorded a stunning 2-1 victory over a Liverpool side who have now managed only one win in eight games in 2017.
Richard Stearman put the visitors ahead after only 53 seconds, left unmarked to head in Helder Costa's free-kick, before Costa set up Andreas Weimann to double Wolves' lead before the break.
Divock Origi pulled one back but Paul Lambert's men held on to fifth round for the first time since 2008.
What is going wrong for Liverpool?
Liverpool manager Jurgen Klopp said: "I am responsible for this performance because I thought this line-up was ready for this game but obviously we weren't and that doesn't feel too good.
"I could look for excuses but I don't want to. Maybe we should use this time to be disappointed, to be frustrated, to be angry at ourselves. All I can say, sorry."
League One Oxford reached the fifth round for the first time in 23 years with a 3-0 win over Championship promotion-chasers Newcastle.
Kane Hemmings met a Chey Dunkley back-post header to put Oxford ahead before Aleksandar Mitrovic missed the chance to level when his penalty was saved low down by Simon Eastwood.
Curtis Nelson added Oxford's second before Toni Martinez sealed a famous win.
"I said to the players at half-time that they wouldn't get a better opportunity to get into the last 16 of the FA Cup," Oxford manager Michael Appleton said.
"For me personally, with the squad Newcastle have got, this surpasses beating Arsenal at Emirates Stadium when I was at Blackburn [in the fifth round four years ago]. That's how big this is.
"It feels fantastic. It won't be long before Newcastle are plying their trade in the Premier League and, with the squad they've got, they'll be challenging in the top half, I believe.
"I think that belief really told in the last 15 minutes and I thought the players were magnificent."
Lincoln City 3 Brighton 1: Non-league Imps shock high-flying Seagulls to reach FA Cup fifth round
For the first time since 1902, Lincoln are in the last 16 of the FA Cup after claiming another Championship victim.
Brighton and Hove Albion have become the latest big-game trophy for the non-League glory hunters after a stirring afternoon at Sincil Bank, providing another sorely needed shot in the arm for the FA Cup.
Seventy-two places may have separated the two clubs but Lincoln, riding high at the top of the National League, assumed the appearance of seasoned veterans as Brighton manager Chris Hughton’s gamble to play an inexperienced team badly backfired.
Lincoln had already beaten Ipswich and Oldham yet this victory, over the Championship leaders, was utterly convincing and will only enhance the burgeoning reputations of manager Danny Cowley and his assistant, brother Nicky.
After dropping out of the Football League six years ago, it is a good time to be a Red Imp.
Cowley, poached from Braintree Town in May, said: “The football gods were smiling on us and it’s difficult to find something profound to say about our run.
“This is a great football club made of great people and it hasn’t had the success that it deserves. The fact we’ve gone on this journey has caught the imagination of the community and we’ve put Lincoln City at the forefront of people’s minds. Hopefully after today we've also captured their hearts.
“The second half was a fantastic performance, we set the benchmark for our levels. The key was to get to 67 minutes and still be in the game, if you do that you’ve got a better chance.
“This wasn’t an 11-man job, this was a club and a city winning a football match.”
It was 41 years ago, under the late Graham Taylor, that Lincoln last reached even this stage of the competition and the dream run has already earned them around £500,000. A plum draw in the last 16 against a Premier League giant could easily take them close towards the million mark.
Over 9,000 people crammed into this old stadium, with Lincoln Cathedral looming large in the distance, and this had all the ingredients for another glorious chapter in the club’s history.
Not even the early setback of going a goal behind threw the non-leaguers out of their stride.
Brighton had made nine changes from the team which beat Cardiff in their last outing and eventually settled on the uneven surface, with midfielder Solly March striking the bar from 30 yards after a mazy run.
And the visiting team temporarily silenced the boisterous home support by taking the lead in the 24th minute.
Glenn Murray nodded Connor Goldson’s long diagonal pass into the path of Richie Towell, who read it brilliantly, and the youngster looped the ball over the advancing Paul Farman.
Game over, you would assume? Not so. Nathan Arnold, the scorer of the goal which dumped out Ipswich in the previous round, forced a spectacular save from Brighton goalkeeper Niki Maenpaa before half-time and optimism was steadily building.
And Lincoln were level 11 minutes into the second period after Murray’s ugly tangle with Theo Robinson in the penalty area, with Maenpaa injuring himself in the melee. Hughton dismissed the penalty decision as “soft”.
The first job for Maenpaa’s replacement, Casper Ankergren, was to take the ball out of the net after Alan Power coolly rolled the penalty into the corner. It was a special moment for Power, who has spent most of his six years at the club struggling outside the football pyramid in front of 2,000 crowds.
Brighton were now wobbling, struggling under the aerial bombardment, and just after the hour Sincil Bank erupted as Fikayo Tomori turned Arnold’s delicious cross into his own net. It summed up a nightmare debut for defender Tomori, signed on loan from Chelsea.
Hughton was shifting uncomfortably in the technical area, struggling to comprehend what was unfolding in front of him.
And Lincoln added the gloss in the 85th minute, Robinson claiming his seventh goal of the season as Brighton’s defence went missing. Robinson, a journeyman forward, is only on a short-term contract but has been offered a longer deal.
The stadium announcer pleaded with Lincoln fans not to run on the pitch as time ebbed away, but it was a futile request. Lincoln are in the last 16.
Hughton defended his team selection, focusing on the poor defending of his team. “It’s a tough weekend for us and a learning curve. Managers who have been in the game for a long time have all been there and it does hurt more to lose a game like this,” he said.
“They capitalised on our mistakes and all three goals were very poor. But it’s a selection I would do again if I had the opportunity. If you make mistakes like we did here, it doesn’t matter whether you’re playing a National League team or one from the Championship.
“I don’t think Lincoln were the better team but I sincerely hope they get a good draw.”
Lincoln City (4-4-2): Farman 7; Wood 7, Waterfall 7, Raggett 7, Habergham 7; Arnold 8, Woodward 7, Power 8 (McCombe 90), Hawkridge 7; Rhead 7 (Long 88) Robinson 8 (Muldoon 87).
Substitutes: Walker (g), Marriott, Miles, Moyses.
Brighton and Hove Albion (4-4-1-1): Maenpaa 6 (Ankergren 57); Tomori 4, Goldson 5, Huenemeier 5, Adekugbe 4; March 5, Sidwell 5, Norwood 5, Skalak 5 (Murphy 68 5); Towell 5 (Hemed 68); Murray 5.
Substitutes: Ankergren (g), Dunk, Kayal, Ince, White.
Booked: Tomori, Murray.
Referee: Andy Madley (West Yorks).